Railway traffic controlling apparatus



y c. B. SHIELDS RAILWAY TRAFFIC CONTROLLING APPARATUS Filed March 19,1941 5 Sheets-Sheet l B B EFS' PVN]? Confpolld b CZCOP oihep y {E manualconiml R O T N v p h 0 Slzzblds HIS Ai'TORNEY May 23, 1944. c. B.SHIELDS RAILWAY TRAFFIC CONTROLLING APPARATUS Filed March 19, 1941 5Sheets-Sheet 2 HIS A'TTORNEY May 23, 1944. I C sHlELDS 2,349,680

RAILWAY TRAFFIC CONTROLLING APPARATUS Filed March 19, 1941 ESheetS-Sheet5 INVENTOR 515 A'II'TORNEY May 23, 1944- c. B. S HIELbS RAILWAY TRAFFICCONTROLLING APPARATUS Piled llarch ,19, 1941 5 Sheets-Sheet 4.

HIS Ai'ToRNEY May 23, 1944. c. B. SHIELDS 2,349,630

RAILWAY TRAFFIC CONTROLLING APPARATUS Filed March 19. 1941 sSheets-Sheet s nsfbound 8DRM 100012 ems I ea/a *Hw 35 4%? I I 20 i E 15'31 g i i v r I L." 7 SW P 8 r- Cozzznol J 0 8mm WFS 89 my mm M 91;Signal a 50' 01217 01190 12 1 C EhCTZCoP othez 89PM WIS manual cont/1'0? INVENTOR' Ch .B. Shzelds BY HIS ATTORNEY Patented May 23, 1944RAILWAY TRAFFIC CONTROLLING APPARATUS Charles B. Shields, Petersburg,Va., assignor to The Union Switch and Signal Company, Swissvale, Pa.-, acorporation of Pennsylvania Application March 19, 1941, Serial No.384,106

Claims. I

My invention relates to railway traffic controlling apparatus of thetype in which coded track circuits are applied to single track, twodirection signaling. More specifically, my invention relates to asignaling system of the above character in which the direction oftraffic is established by a code sent out from a centralized trafiiccontrol location or by other suitable manual control. Accordingly, thedirectional control in the sys tem embodying my invention is notautomatic as in the case of standard A. P. B. circuits.

A feature of my invention is the provision for reversal of trafficdirection without the use of the usual control line wires, by means of amomentary reversal of the track circuit polarity. An-

other feature of my invention is the provision of directional lockingbetween head-block signals so that the traffic direction cannot bereversed or the opposing headblock signal cleared while the section isoccupied by a train. A further feature of my invention i the approachcontrol of the Wayside signals and the train control energy by means ofpolarity selection of the approach code.

One object of my invention is to dispense with all control line wiresexcept the C. T. C. line and toprovide a safe and effective system oftwo direction, single track signaling. A further object of my inventionis to economize electrical energy in the system by providing forapproach control of the wayside and cab signals. A still further objectof my invention is to make use of the same track battery which suppliesthe approach code for supplying the reverse track energy upon a reversalof traffic direction. Other objects, purposes, and features of myinvention will be apparent from the description which follows.

I. accomplishthe foregoing objects by employins a momentary reversal ofthe track circuit polarity which causes an automatic cascading actionover the track circuits of the section and which reverses the enteringand leavin ends of each. track circuit. and. of the stretch.Instrumental in providing this reversal is a. second track relay in.series with the maintrack relay. resnonsive only to the reversetrackcircuit energ whic is. supplied momentarily to. establish the newtra-fii'c direction. The a proach energizaion of wayside and cab signalsis accomplis ed t rough the medium of an approach code which is efective durin the intervals between pulse: of the ordinary signal.control code. When the established. traihc is eastbound. thewestboundsignals will normally be dark, but will display a stopindication to a train moving westbound. A similar operation takes placewhen the established traific is westbound. I accomplish directionallocking between headblocks by providing an approach or VR relay for eachtrack circuit, so controlled that entry of a train drops the first VNrelay, whereupon the action is cascaded to the end of the stretch forgoverning the traffic direction control relay at that end to insure thestop indication of the opposing headblock signal.

I shall describe one form of apparatus embodying my invention, and shallthen point out the novel features thereof" in claims.

Figs. 1a to la, inclusive, of the accompanying drawings when placed endto end with Fig. 1a at the left, are a diagrammatic view showing oneform of apparatus embodying my invention.

Similar reference characters refer to similar parts in each of theseveral drawings.

Referring to the drawings, there is shown a stretch of single trackrailway having a passing siding at each end thereof. This stretch oftrack is divided by means of the usual insulated joints at locations I,Z, 4, 6A, 6, 8, and Ill into track circuit sections 2T, 4T, GA'I, SBT,ST and WT, respectively. Locations I, 2, 4, 6, 8, and it are signallocations whereas 6A is a cut section location which I have introducedto show the apparatus necessary in the case of a block which is verylong. I shall use coded direct current of normal relative polaritysupplied from a suitable battery El for the track circuit control,reversing the polarity of this current momentarily when the direction oftrafiic in the single track stretch is being reversed. Two rates ofcoding, 180 and '75 per minute, respectively, ar supplied by theconstantly operating code transmitters ISUCT and T, only two codes beingrequired for the three-position signaling system illustrated. Sincealternating current'is ordinarily required for operating the locomotivecab signal equipment, I have provided approach energized tunedallternators TA at the various locations for supplying the coded traincontrol energy. For approach control, I make use of a feed back orapproach code supplied from a suitable track battery E2, the impulses ofwhich are eifective during the off intervals of the ordinary trackcircuit code, as will be described hereinafter.

At the left-hand or eastbound end of the stretch. I have provided aneastbound trafiic control relay EFS which may be controlled by a remoteoperator over a C. T. 0. line, or locally by means of a manual lever orother suitable means. A corresponding westbound trallic control relayWFS is shown at the right-hand or westbound end of the stretch. Whenrelay EFS is energized, it initiates a cycle of operation whichconditions the stretch (if unoccupied) for the passage of a train in theeastbound direction. Similarly, energization of relay WFS prepares thestretch for passage of a westbound train.

As shown in the drawings, the headblock signals 2R and BL are at stop.This is also true of the remaining signals except ER and SR which are atclear since the last move through the stretch is assumed to have been inthe eastbound direction. All of the signals are dark, however, since itis assumed that no train is approaching. Code is, however, beingsupplied to the track circuits since these are of the normally energizedtype. At each track circuit junction is a double-wound intermediatepolarized direction selecting relay D which interchanges the enteringand leaving ends of the associated track circuits and thereby determinesthe authorized traific direction in these track circuits. At each end isa double-wound trafiic direction selector (2D and 8D) which initiatesthe reversal of trafiic direction and which controls all of theintermediate direction selecting relays as well as the traffic directionselector at the other end of the stretch.

Looking at Fig. la, the direction selector 2D at that location has, anenergizing circuit for its left-hand winding which includes one terminalB of a source of current, front contact ll of relay EFS, front contactl2 of relay ZVNR, (to be described later), and the other terminal C ofthe source. Relay ZVNR is now deenergized because relay ZVN is notoperating, since front contact IQ of ZDRM is open. Accordingly, contactI2 is open, but selector relay 2D continues to occupy its normalposition because its design is such that it continues to remain in itslast operated position until a reversing impulse is received, whereuponit remains in the reverse position until again restored to normal.. isto say, the D relays are of the polar stick type. As shown, selectorrelay 2D occupies its normal position in which its contact I3v is swungto the left or N position. The closing of contact M of relay 2D preparesan energizing circuit for the right-hand winding of relay 2D so that ifrelay 2RTR should pick up (resulting from traffic reversal fromeastbound to westbound) then selector relay 2D would be reversed by themomentary impulse of current which it would receive over front contact15 of relay 2RTR. and

its own contact Id. The latter contact will imr mediately open, but notuntil a reversal of 2D has occurred and contact Ill is closed in itsright hand or R position.

The impulse relay ZIR. is well known in approach control circuits forcoded wayside signaling. As used herein, this relay when deenergizedconnects the main track relay ZTR and the reverse track relay ZRTR inseries across the track over the back point of its contact H5. and whenenergized, connects the battery E2 which supplies the approach code,across the track. It should be particularly noted that the codefollowing track relays 2TB. and ZRTR- are oppositely poled so that butone of these relays (2TB) will normally follow code. When. the trackcurrent polarity is momentarily reversed, however, relay ZRTR will bepicked up as one step in the trafiic direction changeover.

Relay ZTR controls the usual decoding transformer 2DT over itsperiodically operating contact I1 and so energizes the proceed relay ZJover the resonant decoding unit IBODU. Relay 2J will be picked up on 180code but not on code, in the usual manner. The caution relay 2H islikewise energized from a winding of the decoding transformer EDT overthe rectifying contact I8 of relay 2TB and this relay will be energizedwhenever ZTR is following either or 75 code, but will be deenergizedwhen 2TB, ceases to follow code. The impulse relay 21B. is alsoenergized from the decoding transformer 2DT by means of the winding l9and the intermediate transformer 2!). This transformer is not essentialbut may be used to improve the timing characteristics of relay HR. Theimpulse relay is of the biased polar type (biased to its deenergizedposition) and has a quick response whereby it is capable of followingthe impulses received from the decoding transformer. These impulses are,in effect, cycles of alternating current but the polarized featurepermits the relay to pick up only on half-cycles of positive polarity,as indicated by the plus sign at one terminal of the relay, the biasinsuring that the relay will release during each half-cycle of negativepolarity. This manner of operating the impulse relay is well known andis shown and described in United States Reissue Patent No. 21,- 783granted on April 29, 1941 to Herman G. Blosser for Approach controlapparatus for railway signaling systems.

Relays ZVN and ZVR are polar code following relays which areinstrumental in providing approach control and. also directional lockingbetween the headblock signals. Since Fig. 1a is an end location, theserelays become operative only when relay ZDRM is picked up following areversal of relay 2Dl-t, that is, when front contacts I!) and 20 ofrelay zDR-M become closed and when the back point of contact 2| of thecode transmitting relay 2C'IM is also closed. Accordingly, the VN and VRrelays at the eastbound end will be operative only under westboundtraflic conditions; the VN and VR relays at the westbound end beingoperative only under eastbound traffic conditions which is the directionillustrated in the drawings. At intermediate locations, however, the VNand VR relays will be operative whenever approach or feed back code isbeing received, that is, whenever all the track circuits in advancethereof to the opposing headblock signal are unoccupied. It will benoted that relays ZVN and ZVR are connected in series and are oppositelypoled so that but one of these relays will operate at any given time,depending on the polarity of the feed back code received from the track.Relays 2VNR and 2VRR are merely slow acting repeaters of relays ZVN andZVR, respectively, and these remain constantly picked up provided thatthe respective control contact 22 or 23 is following code.

The tuned alternator ZTA is well known and is shown diagrammatically tosimplify the disclosure. It is shown merely to make the disclosure morecomplete and its purpose is to provide a source of alternating cabsignaling current in the absence of the usual alternating currenttransmission line. This tuned alternator is approach energized, as arethe signals, and it delivers alternating current from its winding ZTASto westbound traffic in track circuit 4T, by virtue of the inclusion ofwinding ZTAS in series with the normal code current supply battery El inthe feed circuit for track circuit 4T when relay {ZDRM is energized andrelay .ZCTM. is .operating.

Having described some of the individual apparatus which enters intotheoperation of my system, I shall now proceed to describe the stepsinvolved in a reversal of trafiic direction in the section and theoperations which take place as a train progresses through the section.As the apparatus stands, normal signal control code is being supplied totrack circuit 8T from battery El by the coding action of relay 8CIM andthis code is cascaded over the track circuits to the castbound .end in amanner to be described hereinafter. Relay Z'IR follows code and operatesrelayL2IPt which supplies feed back code from battery E2 to the trackcircuit 4T, from which the feed back code is cascaded to the westboundend Where it operates relay BVN, causing relay BVNR to be energized.

Since the drawings show the apparatus set up for an eastbound move, Ishall assume that it is desired to reverse the traffic direction topermit a westbound train to pass over the stretch. To do this, theoperator will send out a suitable C. T. C. code which will pick up thewestbound stick relay W'FS at the westbound end of the stretch shown inFig. 19. Since relay BVNR is energized, the pickup of relay WFS willreverse trafiic direction selector relay 8D to the right because theright-hand winding of this relay will now become energized over frontcontact 24 of WFS and front contact 25 of BV'NR. Signal 8R. being atstop, its home relay BRAH (the control of which is well known) will bedeenergized so that back contact 26 will be closed. Just prior to thereversal of relay 8D, the code transmitting relay 8CTM will be operatingon '75 code by virtue of the 75 code circuit which extends from oneterminal B, contact 2! of code transmitter 'HECT, back contact 26 ofrelay BRAH, and normal contact 23 of relay 8D, to the other terminal C.As will be shown hereinafter, the supply of '75 code to section 8Tcauses 180 code to be supplied to section BBT and cascaded to theeastbound end from which a 180 feed back code is cascaded back tosection 8T. Relay SVN is now following these impulses of 180 feed backcode and so causes its repeater BVNR to remain energized due to codeoperation of front contact 29 of relay Relay BVNR, when energized,checks that no train is occupying the section between signals 2L and 8R,and also that the track circuit ET is unoccupied and signal 2R is atstop so that its locking relay ZRMS is energized.

As soon as relay 8].) reverses, relay liCTM ceases to follow code andrelay BDRM is picked up over contact 39 of relay 8D, now in its reverseposition. The pick-up of SDRM closes the front points of contacts 31 and32 so that an impulse of feed back energy can be received from sectionBT by relay 8TH. A feed back impulse will be transmitted to section 8Teven after normal code to this section is discontinued and relay 6TB,has released because the last release of 6TB. will p ck up the impulserelay SIR which will then transmit the feed back impulse from. batteryE2 over the front point of contact Ml. Operation of relay 8TR by thisimpulse of feed back energy causes response of impulse relay 81Rwhereupon a current impulse of reverse polarity is supplied from batteryE2 to the track circuit 8T over the front contacts 33 and 34, and 35 and36, of relays IBCDR and BLMS, respectively. Relay HICDR is merely a codedetection relay for track circuit HIT and detects the unoccupiedcondition of this track circuit. The locking relay iiLMS checks the stopindication of headblock signal 8L and is energized when and only whenthis signal is at stop.

The reverse Current impulse transmitted over the front contact l5 ofrelay 81R from battery E2 is received by reverse track relay GRTR atlocation 6 and it will be noted that this relay is poled in such adirection as to be operated by an impulse of reverse polarity but not of.normal polarity, the latter impulses operating relay 6TB only. Thepick-up circuit for relay BRTR may b traced from the upper track rail,wire 31, back contact 38 of relay BDRM, wire 39, back point of contactMl of relay 61R, wire M, relays 6TB. and BRTR, wire 42, back contact 43of relay BDRM, and wire 44, back to the lower rail.

When relay BRTR picks up, it closes the reverse energizing circuit forrelay 6D over a path which includes front contact 45 or ERTR, wire 46,normal contact 41 of relay 6D, wire 48, righthand winding of relay 6D,and front contact 49 of relay BVNR. The reversal of relay 5D causespick-up of relay SDRM over contact 59 of relay 6D in its reverseposition, whereupon a holding circuit is established for relay 61R overfront contacts 5.! and 52 of relays EDRM and SDM, respectively. Thisholding circuit includes the lower winding of relay 61R and issufiicient to maintain this relay energized irrespective of whether theupper winding is or is not energized. Pick-up of 61B. causes a reversecurrent impulse to be transmitted from battery E2 to the track circuitGBT over a path which includes one terminal of the battery, wire 53,front point of con-- tact 5d of BVNR, wire 55, front point of contact 56of GDRM, wire 5i, upper rail of track circuit 613T, lower rail, wire 58,front point of contact 59 of EDRM, Wires 69 and 33, front point ofcontact 40 of 61R, wire ti, and front point of contact 62 of tVNR. tothe other terminal of battery E2.

At the cut section location 6A, the response of relay 6ARTR to thereverse code impulse and the consequent reversal of relay tAD andpick-up of relays BADRM, tADM, and EAIR will be clear from the previousdescription so that this description need not be repeated. Accordingly,it will be clear that a reverse code impulse will be transmitted intotrack circuit -BAT and finally into track circuit 4T, so that the actionwhich was initiated through the pick-up of relay WFS at location 8 whichresulted in the application of reverse current to the first westboundsection has been cascaded over each intervening track circuit, in turn,until th first eastbound section 4T has been reached. This cascadingaction provides assurance that the stretch is unoccupied becauseotherwise, the reverse code could not pass beyond the occupied trackcircuit.

At location 2, relay ZRTR will respond to the reverse code impulse andwill reverse relay 2D over its front contact l5 and the normal contact Mof relay 213. When this happens, the control circuit for the eastboundheadblock signal 2R will be interrupted at normal contact 63 of relay 2Dand a 75 code operating circuit will be established for relay ZCTM overcontact 64 of relay 2D in its reverse position and the back point ofcontact 65 of lock relay ZLAH for signal 2L. Since relay ZDRM is nowpicked up, normal polarity 75 code from battery E! is supplied to thetrack circuit 4T over the front point of contact 2| of relay ZCTM. This75 code causes response of relay 4TB at location whereupon relay 4Hpicks up and closes the 180 code circuit for relay 4CTM over the frontpoint of contact 66, wire 61, 180 code contact 68, and wire 69. The 180code will be relayed into track circuit EAT by virtue of the operationof contact of relay 4CTM which codes the current from battery El. Atlocation 6A, the front point of contact H of relay 6ATR will relay the180 code into track circuit GBT in an obvious manner. The cascading ofthe normal code into track circuit 8T will be clear from the foregoing.

At location 8, since relay BDRM is picked up, relay 8TB will receive andfollow the 180 code so that relays SJ and 8H will both be energized andwestbound headblock signal 8L will be cleared over a circuit whichincludes front contact 12 of relay 8H, reverse contact '13 of relay 8D,and the front point of contact M of relay 8J. The clearing of thissignal indicates that the stretch between headblock signals isunoccupied; that all of the D relays have been reversed and that thetrack circuits are in proper working order since code has been cascadedto the new entering end; and that the opposing headblock signal is atstop. Since relay BTR is now operating and relay BDRM is up, feed backor approach code of normal polarity for the approach energization of thesignals will be supplied to section 8T over the front contact 15 ofrelay 81R and this code will be cascaded to the eastbound end since eachof the intermediate TR relays is operating. The DRM relays being up, theapproach relay VN at each location will be energized because the feedback code is of normal relative polarity for selectively operating theVN relays.

I shall now assume that a westbound train passes signal 8L and enterstrack circuit MT. The code detecting relay IUCDR will be released sothat battery E2 will now supply an approach code of normal polarity(reverse polarity feed back code having been previously supplied fromthis battery prior to entry of the train) this normal polarity codebeing supplied over the back points of contacts 33 and 34 of relayIEJCDR, coding contact 15 of relay 81R, and front points of contacts 3|and 32 of relay BDRM. Since relays GVN and [WE at location 6 areoppositely poled, the normal polarity approach code will cause relay 6VNto release and relay BVRto follow the code. The release of GVN releasesBVNR due to opening of contact 16, and consequently pole-changes thereverse code supplied from battery E2 at that location to the trackcircuit GBT. This approach code of normal polarity is thus cascaded overeach intervening track circuit to track circuit 4T,

so that all of the VN relays ahead of the train will drop and all of theVR relays will be picked up. In this manner, directional locking betweenheadblock signals is obtained because the direction selecting relay Dcannot be reversed, once a train enters the stretch, due to the factthat this relay is controlled over a front contact of the VNR relaywhich is a repeater of the VN r lay, now deenergized.

Referring again to the entry of the train into the track circuit IDT,once the train passes location 8, the approach code received by relayBVR at location 6 will be shunted so that both relays SVR and GVRR willrelease, relay GVNR having been previously released. This results in theenergization of the tuned alternator STA over the back contacts '71 and18 of relays BV'RR and SVNR which results in the supply of train controlcurrent, coded at the proper rate by relay SCTM, from the winding BTASto the track rails of section 8T ahead of the train. Also, the proceedaspect of signal 6L will now be displayed because of the closing of theclear signal circuit as follows: from one terminal +LB, back contact 19of relay SVNR, back contact of relay SVRR, wires 8|, 82, and 83, frontpoint of contact 84 of relay GDRM, and front points of contacts 85 and86 of relays 6H and BJ, respectively, to the proceed unit of the signal6L and terminal LB.

When the train enters the track circuit BBT, train control energy willbe fed towards the train in a similar manner from the winding GATAS ofthe tuned alternator at location 6A. The clear ing of signals 4L and 2Lwill occur in a similar manner to that described for signal 6L and sothis description need not be repeated.

From the foregoing description, it will be apparent that I have providedan effective signaling system for two direction running on single track,with approach control and directional looking, all without the use ofcontrol line wires. Also, I have employed only the usual and '75 codeswhich provide three position signal aspects, but by transmitting thesecodes both'in the normal and in the reverse direction under proper trackcircuit conditions and by making selective use of current polarity inthese codes, I have provided a system in which the traffic directionreversa1 and passage of traffic in the new direction is readily andsafely accomplished.

Although I have herein shown and described only one form of apparatusembodying my invention, it is understood that various changes andmodifications may be made therein Within the scope of the appendedclaims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is: I

1. In combination with a stretch of track over which traflic may move ineither direction, said stretch being divided into a plurality of trackcircuit sections, an eastbound and a westbound polarized trafiicdirection selector at the respective ends of said stretch, a polarizedtraflic direction relay at the junction of each pair of said trackcircuit sections, an eastbound and a westbound headblock signal at therespective ends of said stretch, means governed by said westboundselector when occupying its normal position for supplying coded currentof normal relative polarity to the end track circuit at the westboundend and for maintaining said westbound signal at stop, means forcascading said coded current over the remaining track circuits of saidstretch to the eastbound end, means efiective when said eastboundselector occupies its normal position and said coded current iseffective in the section at said eastbound end for conditioning saideastbound signal to display its proceed indication, means at saideastbound end effective for sup plying feed back code impulses to saidend track circuit during the off intervals of said coded current tomaintain the adjacent traffic direction relay in its normal position,means including said last-mentioned relay for cascading said feed backcode over the remaining track circuits to said westbound end to maintainthe remaining trafiic direction relays in their normal position andprovide approach energization for eastbound trafiic moving over saidstretch, and means effective upon a reversal of said westbound selectorfrom its normal to its reverse position for supplying an impulse ofreverse relative polarity to the section at said westbound end toreverse all of said traihc direction relays including said eastboundselector in sequence to thereby place said eastbound signal at stop andcondition said westbound signal to display its proceed indication.

2. In combination with a stretch of track over which traflic may move ineither direction, said stretch being divided into a plurality oftrackcircuit sections, an eastbound and a westbound headblock signal at therespective ends of said stretch, a mainand an auxiliary track relay foreach of said sections receiving energy from the rails thereof andselectively responsive to current of normal and reverse polarityrespectively, a-trafiic direction selector having a normal position forsetting said westbound signal at stop and for applying coded current ofnormal relative polarity to the westbound end section, said currentbeing cascaded from the westbound to the eastbound end of said stretchby virtue of the response of the main track relays sequentially thereto,means controlled by the last main track relay for conditioning saideastbound si nal to indicate proceed, means efiective upon a reversal ofsaid trafiic direction selector for supplying an impulse of current ofreverse relative polarity to said westbound end section for operatingthe auxiliary track relay associated there'- with, said reverse polarityimpulse being cascaded to the eastbound end of said stretch by virtue ofthe response of said auxiliary track relays sequentially thereto, thelast auxiliary relay setting said eastbound signal at stop, and meanscontrolled by said last auxiliary relay for causing coded current to becascaded from said ea'stbound to said westbound end for clearing saidwestbound headblock signal.

3. In combination with a stretch of track over which traffic may move ineither direction, said stretch being divided into a plurality of trackcircuit sections, an eastbound and a westbound headblock signal at therespective ends of said stretch, amain and an auxiliary code followingtrack relay for each of said sections connected in series'and normallyreceiving coded current from the associated section, said relays beingselectively responsive to current of normal and reverse polarityrespectively, an eastbound and a westbound traific direction selector atthe respective ends of said stretch each having a normal and a reverseposition for establishing eastbound and westbound traffic directionrespectively over said stretch, means controlled by said westboundselector when normal for placing said westbound headblock signal at stopand for supplying coded current of normal relative polarity to the trackcircuit at that end for operating the main track relay associatedtherewith, said main track relay causing coded current to be cascadedover the remaining track circuits by virtue of the operation of theremaining main track relays, means controlled by the last main trackrelay and by said eastbound selector when normal for conditioning saideastbound headblock signal to indicate proceed, other means controlledby said last main track relay 'for cascading impulses of an approachcode over the track circuits from the eastbound to the westbound end ofsaid stretch during the off intervals of said coded current, meanseffective when said westbound selector is moved to its reverse positionfor transmitting a reverse polarity impulse to the track circuit at thewestbound end for operating the auxiliary track relay associatedtherewith, said reverse polarity impulse being cascaded over theremaining sections'by the intervening auxiliary relays to operate thelast auxiliary tracl: relay, and means controlled by said last auxiliarytrack relay for causingsaid eastbound selector to assume its reverseposition and so to reverse the direction of trafiic over said stretch.

4. In combination with a stretch of track over which traflic may move ineither direction, said stretch being divided into a plurality of trackcircuit sections, an eastbound and a westbound headblock signal at therespective ends of said stretch, a manually controlled selector having anormal position for eastbound trafiic and a reverse position forwestbound traffic, means controlled by said selector when normal forplacing said westbound headblock signal at stop and for supplying codedcurrent of normal relative p0- larity to the westbound end trackcircuit, said current being cascaded over the track circuits to theeastbound end to thereby check the unoccupancy of said stretch, a normalcode following track relay at the eastbound end selectively responsiveto said coded current of normal polarity for conditioning said eastboundsignal toindicate proceed, means efiective when said manually controlledselector is reversed for supplying an impulse of current of reverserelative polarity to said westbound end track circuit, a reverse codefollowing track relay for said last-men'- tioned track circuitselectively responsive to said reverse polarity impulse, and meanscontrolled by said reverse track relay for setting said eastbound signalto stop and for conditioning said westbound signal to indicate proceedto thereby reverse the direction of trafiic over said stretch.

5. In combination with a stretch of railway track over which traffic maymove in either. direction, said stretch being divide'd into a pluralityof track circuit sections, an eastbound and a westbound headblock signalat the respective ends of said stretch, an eastbound and a' westboundmanually controlled selector at the respective ends of said stretch eachhaving a normal position for eastbound trafiic and a reverse positionfor westbound trafiic, a-normal code following track relay and a reversecode following track relay for each track circuit selectively responsiveto current of normal and reverse polarity respectively, a polarizedtrafic direction'relay for each track circuit normally occupying itsnormal position and caused to assume its reverse position in response tocode following operationof its associated reverse track relay, meanscontrolled by said westbound selectorwhen normal for setting saidwestbound signal at stop andfor supplying coded current of normalrelative polarity to the westbound end track circuit to thereby'operatethe normal track relay associated therewith and cause coded current tobe cascaded over said'sections to the eastbound end; means controlled bythe last normal track relay and by said eas bound selector forconditioning said eastbound signal to indicate proceed and-forsu-pp'lyingcurrent impulses to the-sections of said stretch for approachcontrol, s'a'id' current impulses being supplied during the ofiintervals ofsaid coded current, means effective when said westboundselector is reversed for supplying a reverse polarity impulse to thewestbound end track circuit to operate the associated reverse trackrelay and so to reverse the polarized direction relay associatedtherewith, means controlled by said lastmentioned relay and includingthe remaining reverse track relays for cascading said reverse impulse tothe eastbound end, and means co'ntrolled by the last reverse track relayfor reversing said eastbound selector to thereby complete the reversalof trafiic direction over said stretch.

6. In combination with a stretch of track over which traffic may mov ineither direction, said stretch being divided into a plurality of trackcircuit sections, a manually controlled traffic direction selector atone end of said stretch, means controlled by said selector when normalfor supplying coded current to the track circuit at that end of thestretch and cascading the coded current over the remaining trackcircuits to the other end to check unoccupancy of the stretch, means forsupplying impulses of normal polarity feed back code during the offintervals of said coded current to the end track circuit at said otherend and cascading said feed back code over said stretch by means of afirst code responsive relay associated with each section and selectivelyresponsive to said normal polarity code, a second code responsive relayfor each section arranged in energy receiving relation with the trackand selectively responsive to feed back code of reverse relativepolarity, means effective when a train enters said stretch at said oneend and releases said first code responsive relay associated therewithfor pole changing the feed back code supplied to the next section inadvance to thereby operate said second code responsive relay for thenext section and so to provide approach energization, and meanseffective upon a reversal of said traffic direction selector formomentarily reversing the polarity of said first-mentioned coded currentto thereby operate traflic direction selecting apparatus for eachsection and so to reverse the traflic direction in said stretch.

7. In a two direction single track system of signaling, a track circuitat the entering end of the stretch for a given direction of traflicmovement, means including a two-position traffic direction selector inits normal position for supplying coded current of normal relativepolarity to said track circuit at the entering end thereof, means forsupplying feed back code during the off intervals of said coded currentto said track circuit at the leaving end thereof provided said singletrack stretch is unoccupied, a control relay energized in response tothe presence of said feed back code, a polarized traffic direction relayenergized over a front contact of said control relay to thereby preventreversal of said traflic direction relay during occupancy of said trackcircuit and so to provide directional locking, means efiective upon areversal of said traflic direction selector for momentarily reversingthe polarity of said first-mentioned coded current, and a reverse trackrelay for said track circuit selectively responsive to said reversepolarity current for reversing said polarized relay to thereby reversethe trafiic direction over said track circuit.

8. In a two direction single track system of signaling, a track circuitat the enterin end of the stretch for a given direction of traificmovement, means including a manually controlled two position trafiicdirection selector in its normal position for supplying coded current ofnormal relative polarity to said track circuit for controlling trafficmovement in said given direction over said track circuit, a polarizedreverse track relay for said track circuit, a polarized trafficdirection relay for said track circuit controlled over a front contactof said reverse track relay, means eifective upon a reversal of saidtrafiic direction selector for momentarily reversing the polarity ofsaid coded current to thereby operate said reverse track relay and so toreverse said trafiic direction relay, and means controlled by saidtraific direction relay for reversing the trailic direction over saidtrack circuit.

9. In a two direction single track system of signaling, a. track circuitat the entering end of the stretch for a given direction of trafficmovement, means including a two position traflic direction selector inits normal position for supplying coded current of normal relativepolarity from a first source to said track circuit at the entering endthereof for controlling trafiic movement in said given direction oversaid track circuit, a polarized reverse track relay for said trackcircuit, means effective upon a reversal of said traffic directionselector for momentarily supplying an impulse of reverse relativepolarity from a second source to thereby operate said reverse trackrelay, means controlled by said reverse track relay for reversing thetraffic direction in said track circuit, and means controlled by saidselector when reversed and effective when the trafific direction hasbeen reversed for supplying an approach code from said second source tosaid track circuit.

10. In a two direction single track signaling system, a track circuit atthe entering end of the stretch for a given direction of traflicmovement, a two position traffic direction selector, a code followingrelay, means including a normal contact of said selector for supplyingcode to said relay to cause code following operation thereof, apolarized approach relay, means including a contact of said codefollowing relay and effective when said selector is normal foralternately supplying coded current of normal relative polarity to saidtrack circuit at the entering end thereof and connecting said approachrelay to receive approach code impulses therefrom, said approach codeimpulses being supplied during off intervals in said coded currentprovided the stretch beyond said track circuit is unoccupied, apolarized normal track relay associated with said track circuit at theentering end thereof, a polarized reversed track relay associated withsaid track circuit at the leaving end thereof, means effective when saidselector is reversed for connecting said normal track relay with saidtrack circuit to cause operation thereof on an impulse of said approachcode, means effective when said normal track relay is operated forsupplying an impulse of reverse relative polarity to said track circuitto operate said reverse track relay, and a, traffic direction governingrelay for said track circuit controlled by said reverse track relay.

CHARLES B. SHIELDS.

